1. Field of the Invention
The present invention relates to integration of high-voltage devices and low-voltage devices, and more particularly, to a method for fabricating high-voltage semiconductor devices having a trench structure.
2. Description of the Prior Art
As the scale of integrated circuits (ICs) has been rapidly decreased, the design and layout rule becomes more stringent. Moreover, as the integrated circuits (ICs) are fabricated to be more compact, the integration of ICs with different application becomes indispensable.
FIG. 1 shows the cross section of a conventional high-voltage complimentary metal-oxide-semiconductor (HV-CMOS) transistor, which usually includes a p-type substrate 10, field oxide regions 4, an n.sup.+ source region 2, an n.sup.+ drain region 2A, a gate region 3, and an oxide layer 5. In the structure of the shown transistor, the structure of its drift region generally adopts conventional local oxidation (LOCOS) technique, which has a horizontal or lateral configuration. On the other hand, low-voltage semiconductor devices in the deep-submicron semiconductor technology (e.g., less than 0.25 micrometer) largely utilize trench oxide structure, which has a vertical configuration, to save chip area. Accordingly, in the present semiconductor industry, the difference of the used configuration becomes a bottleneck for the integration of the high-voltage devices and the low-voltage devices. Moreover, the conventional high-voltage devices suffer current driving capability when the structure is scaled down.
For the foregoing reasons, there is a need for disclosing a structure and a method of fabricating high-voltage semiconductor devices having an improved current driving capability, and facilitating the integration with the low-voltage semiconductor devices.